Rubber cylinder having higher hardness in upper end portion, packer, and bridge plug

ABSTRACT

A hardness of an upper end portion of a rubber cylinder is greater than a hardness of a middle portion, so that when the upper end portion bears a first axial pressure, the deformation of the middle portion in a radial direction is greater than the deformation of the upper end portion in the radial direction. A packer and a bridge plug include the rubber cylinder. The hardness of the upper end portion is greater than the hardness of the middle portion. When the upper end portion is subject to the first axial pressure, the upper end portion more likely transfers the first axial pressure to the middle portion and a lower end portion instead of deforming radially itself. A relatively small first axial pressure can be used to enable the middle portion and the lower end portion to deform radially, thereby achieving an overall seal of the rubber cylinder.

TECHNICAL FIELD

The invention relates to the field of sealing, and in particular, to a rubber cylinder having a higher hardness in an upper end portion, a packer, and a bridge plug that are used in the petroleum production industry and can withstand high temperature and high pressure.

BACKGROUND OF THE INVENTION

Packers are critical tools used for downhole production in oil fields, and are widely applied to various works such as oil field injection, separated-zone transformation, separated-zone production, and mechanical channel plugging. A packer needs to provide an annular seal to implement oil-gas separation. A rubber cylinder is a core component for implementing an annular seal. A bridge plug is also a commonly used oil-gas separation tool in production work. A major difference between a packer and a bridge plug lies in that a packer is usually kept in a well temporarily during operations of measures such as fracturing, acidising, and leakage finding. A bridge plug is temporarily or permanently kept in a well during measures such as isolation of a zone for production. A packer is kept in a well together with a central tube. When being equipped with a release, a packer can be separately kept in a well. A bridge plug can be separately kept in a well. Structurally, a packer has a hollow structure in which oil, gas or water can flow freely, whereas a bridge plug is a solid structure.

As oil-gas separation tools, both a packer and a bridge plug need a rubber cylinder. A rubber cylinder is a critical component for sealing. The sealing effect and service life of a packer and a bridge plug directly depend on the quality of a rubber cylinder, which is therefore critical for a packer and a bridge plug. The name is “rubber cylinder” because a rubber cylinder is usually made of a rubber material. However, “rubber cylinder” is only a technical term commonly accepted in the industry and used to represent a functional component having a sealing effect, but does not only indicate that a rubber cylinder can be made of rubber only. When a rubber cylinder bears a particular pressure and therefore deforms for sealing, the deformability of the rubber cylinder needs to be considered. If deforming insufficiently, the rubber cylinder cannot produce a sealing effect. If deforming excessively, the rubber cylinder may collapse and fail, and loose recover ability. The most important part is that when a rubber cylinder is exposed to high-temperature steam in a well, the rubber cylinder will fail and loose recover ability more, since it is affected by both high temperature and high pressure.

Issue 1 (2013) of Oil Field Equipment discloses an article entitled Analysis of Comparative Advantage and Structure Improvement of Packer Rubber, in which the following content is recorded: “Three rubber cylinders are sleeved on a common packer, and two structural forms are comprised. In one structural form, an upper rubber cylinder, a middle rubber cylinder, and a lower rubber cylinder have the same size. In the other structural form, an upper rubber cylinder and a lower rubber cylinder are long rubber cylinders, and a middle rubber cylinder is a short rubber cylinder. It is found by researching a conventional three-rubber-cylinder structure that the upper rubber cylinder produces the primary sealing effect”. Moreover, it is found by performing nonlinear analysis by using the nonlinear finite element analysis software Abaqus that: “As the axial load increases, the axial compression amount also increases. The increase of the compression amount is relatively obvious at the beginning. The increase of the compression amount slows down later, and the deformation of the rubber cylinder tends to be stable. As the setting force increases, the length of contact between the rubber cylinder and the casing gradually increases. The radial deformation of the outer column surface part of the rubber cylinder is restricted, and the deformation of the inner surface of the rubber cylinder protrudes outwardly as the outer surface. When the load increases, the rubber cylinder is flattened and is eventually compacted. However, due to structural limitations, only the upper rubber cylinder can be compacted. When the operating pressure is 30 MPa, the upper rubber cylinder is basically completely compacted. A slightly extruded shoulder appears at an upper end of the rubber cylinder, but a rupture phenomenon does not occur in the rubber cylinder. The extruded shoulder is within an allowable range”.

Only the application of a first axial pressure (equivalent to the “axial load”) from top to bottom to a rubber cylinder has been analysed in the foregoing prior art. However, during actual production, one first axial pressure needs to be first applied to the rubber cylinder to enable the rubber cylinder to create a seal. The rubber cylinder is then subject to one second axial pressure (the impact on the rubber cylinder by a substance such as a downhole gas) from bottom to top. According to experiments by the inventors, when the axial operating pressure is 30 MPa, the inventors find that extruded shoulders appear on almost all upper rubber cylinders. When the second axial pressure (for example, 15 MPa) is then further applied from bottom to top, ruptures occur at the extruded shoulders of all the upper rubber cylinders, causing the seal to fail.

SUMMARY OF THE INVENTION

One objective of the invention is to provide a rubber cylinder having a new structural design, to prevent a seal of a rubber cylinder from failing.

According to an aspect of the invention, a rubber cylinder is provided, the rubber cylinder having a through hole located at the centre, an inner surface located at the through hole, an outer surface corresponding to the inner surface, an upper end portion and a lower end portion respectively located at two ends of the rubber cylinder, and a middle portion located between the upper end portion and the lower end portion, the upper end portion being used to bear a first axial pressure in an axial direction, and the lower end portion being used to bear a second axial pressure opposite to the first axial pressure in the axial direction; when the first axial pressure is applied to the upper end portion, the upper end portion, the middle portion, and the lower end portion all deforming in a radial direction; and when the second axial pressure is applied to the lower end portion, the upper end portion, the middle portion, and the lower end portion all deforming in the radial direction, wherein a hardness of the upper end portion is greater than a hardness of the middle portion, so that when the upper end portion bears the first axial pressure, the deformation of the middle portion in the radial direction is greater than the deformation of the upper end portion in the radial direction.

According to another aspect of the invention, a packer is provided, the packer having the rubber cylinder defined in one of the foregoing technical solutions.

According to still another aspect of the invention, a bridge plug is provided, the bridge plug having the rubber cylinder defined in one of the foregoing technical solutions.

The technical solutions provided in the present application at least have the following technical effects:

According to the technical solutions of the present application, the hardness of the upper end portion is greater than the hardness of the middle portion. In this way, when the upper end portion is subject to the first axial pressure, the upper end portion more likely transfers the first axial pressure to the middle portion and the lower end portion instead of deforming radially itself. In this way, when a relatively small first axial pressure is used, the middle portion and the lower end portion can deform radially, to achieve an overall seal of the rubber cylinder.

According to the technical solutions of the present application, if the hardness of the middle portion is kept unchanged, in the present application, the hardness of the upper end portion is set to be greater than the hardness of the middle portion. In this way, under the effect of the same first axial pressure, the deformation of the upper end portion in the radial direction is relatively small. It should be particularly noted that correspondingly an extruded shoulder formed on the upper end portion due to radial deformation is also relatively small. The relatively small extruded shoulder can effectively prevent the rubber cylinder from rupturing, thereby achieving the effect of preventing the seal of the rubber cylinder from failing.

In an embodiment, because a base body comprises a plurality of filaments, a seal ring is slightly harder when a quantity of filaments is relatively large, and a seal ring is slightly softer when a quantity of filaments is relatively small. In this way, a hardness of a seal ring can be adjusted according to the quantity of filaments. In this way, the overall hardness of a rubber cylinder can be directly changed by changing a hardness of a seal ring, thereby achieving the objective of expanding the compressive strength range of the rubber cylinder.

The base body of the present application has filaments intersecting each other, and a colloid bonds all the filaments. When the rubber cylinder expands under the first axial pressure, the filaments restrict the expansion, so as to increase the overall structural hardness of the rubber cylinder, thereby increasing the compressive strength of the rubber cylinder.

A plurality of seal rings used in the present application is axially arranged. If an individual seal ring is damaged during petroleum production, the damaged seal ring may be replaced with a new seal ring, and the remaining seal rings are not replaced. In this way, on the whole, by using the axial arrangement of the plurality of seal rings, the average use duration of a single seal ring is increased, so that the usage of rubber cylinders can be greatly reduced and production costs can be reduced.

When a packing is chosen for the base body of the present application, an existing high-temperature high-pressure resistant packing may be chosen. In this way, when a colloid is combined with a graphite packing or a carbon fibre packing to form a seal ring, the entire packing can produce a support effect, and the colloid can produce the effects of deformation and sealing enhancement. An existing packing is chosen in the invention, and a dedicated packing to be used as the base body does not need to be fabricated, so that the flexibility of production can be improved. As far as the inventors are aware, an existing graphite packing and an existing carbon fibre packing can withstand the effects of high temperature and high pressure, but have relatively poor resilience. In the present application, the colloid is dispersed in the packing, and the colloid facilitates the recovery of the compressed packing after the first axial pressure disappears, making it easy to remove the rubber cylinder from a borehole.

An angle is formed between the base body of the present application and the radial direction of the rubber cylinder. In this way, when the rubber cylinder is subject to the effect of the first axial pressure, a seal ring becomes parallel to the radial direction of the rubber cylinder before starting to protrude inwardly and outwardly in a radial direction. When turning from an inclined state to a state of being parallel to the radial direction, the seal ring does not deform in the radial direction, and only the rubber cylinder deforms in the radial direction. In this way, on the whole, an angle between the base body and the radial direction of the rubber cylinder increases a deformation amount in the radial direction of the rubber cylinder, so that the defect of insufficient deformation of the rubber cylinder in the radial direction because of relatively high hardness can be overcome.

The above-mentioned description is merely a summary of the technical solutions of the invention. In order to more clearly understand the technical means of the invention so that the implementation can be carried out according to the content of the description, and in order to make the above-mentioned and other objects, features and advantages of the invention be more comprehensible, the particular embodiments of the invention will be illustrated below.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings described herein are used to provide a further understanding of the invention and constitute a part of the invention, and the schematic embodiments of the invention and the description thereof are used to explain the invention and do not constitute an improper limitation on the invention. In the drawings:

Some of the particular embodiments of the invention will be described below in detail in an exemplary but not limiting way with reference to the accompanying drawings. The same reference signs indicate the same or similar components or parts in the accompanying drawings. In the accompanying drawings:

FIG. 1 is a schematic view of a position relationship between a compression packer comprising a rubber cylinder according to an embodiment of the invention and a central tube and a casing;

FIG. 2 is a schematic view of a position relationship between a rubber cylinder according to an embodiment of the invention and a central tube and a casing, wherein only a part of the rubber cylinder, the central tube, and the casing is shown;

FIG. 3 is a schematic view of a position relationship between an extruded shoulder generated after a first axial pressure is applied to the rubber cylinder shown in FIG. 2 and the central tube and the casing, wherein at this time a second axial pressure has not been applied to the rubber cylinder yet;

FIG. 4 is a schematic structural view of a rubber cylinder according to an embodiment of the invention;

FIG. 5 is a schematic structural view of a seal ring according to an embodiment of the invention;

FIG. 6 is a schematic structural view of a rubber cylinder according to another embodiment of the invention;

FIG. 7 is a schematic structural view of a rubber cylinder according to still another embodiment of the invention;

FIG. 8 is a schematic structural view after the rubber cylinder shown in FIG. 6 and FIG. 7 is compressed by a first axial pressure;

FIG. 9 is a schematic structural view of a constraining casing used in an embodiment of the invention;

FIG. 10 is a schematic structural view of a rubber cylinder comprising a constraining casing according to an embodiment of the invention, showing a position relationship between the constraining casing and other parts of the rubber cylinder before compression;

FIG. 11 is a schematic structural view of the rubber cylinder in FIG. 10 during compression by a first axial pressure;

FIG. 12 is a schematic structural view of the rubber cylinder in FIG. 10 after compression by a first axial pressure, showing a position relationship between the constraining casing and the other parts of the rubber cylinder after compression; and

FIG. 13 is a schematic structural view of a three-section rubber cylinder according to an embodiment of the invention.

The reference numerals in the drawings are as follows:

-   -   10—Rubber cylinder, 101—Outer surface, 102—Inner surface,         103—Through hole, 104—Upper end portion, 105—Lower end portion,         106—Middle portion, and 107—Extruded shoulder;     -   108—Base body, 109—Colloid, 111—Seal ring;     -   20—Constraining casing, 21—Necking end, and 22—Flaring end;     -   30—Central tube;     -   40—Casing;     -   50—Stiff spacer ring;     -   60—Protrusion;     -   200—Compression packer;     -   A—First axial direction;     -   B—Second axial direction;     -   F₁—First axial pressure; and     -   F₂—Second axial pressure.

DETAILED DESCRIPTION OF THE INVENTION

The directions “up” and “down” hereinafter are both described with reference to FIG. 2.

A compression packer 200 shown in FIG. 1 has a rubber cylinder 10 of the present application. The compression packer 200 is connected to a central tube 30 and is placed inside a casing 40. The compression packer 200 needs to separate different oil-bearing layers and water-bearing layers in a wellbore and bear particular pressure differences. It is required that the compression packer 200 can reach down a predetermined position in a wellbore and provide tight sealing, and is durable in a downhole and can be successfully removed as required.

As shown in FIG. 2, the rubber cylinder 10 is located in an annular gap formed by the casing 40 and the central tube 30. A stiff spacer ring 50 provides a first axial pressure F₁ from top to bottom (that is, a first axial direction A) in an axial direction. In another embodiment, the stiff spacer ring 50 may further be omitted and replaced by another component that can apply the first axial pressure F₁ to the rubber cylinder 10. As shown in FIG. 2, two ends of the rubber cylinder 10 are an upper end portion 104 and a lower end portion 105, and a middle portion 106 is located between the upper end portion 104 and the lower end portion 105. The upper end portion 104 is used to bear the first axial pressure F₁ in the axial direction, and the lower end portion 105 is used to bear a second axial pressure F₂ opposite to the first axial pressure F₁ in the axial direction. As parts of the rubber cylinder 10, the upper end portion 104, the lower end portion 105, and the middle portion 106 should all have elasticity. As an explanation, when the first axial pressure F₁ is applied to the upper end portion 104, the upper end portion 104, the middle portion 106, and the lower end portion 105 all deform in a radial direction; and when the second axial pressure F₂ is applied to the lower end portion 105, the upper end portion 104, the middle portion 106, and the lower end portion 105 all deform in the radial direction. In the embodiment shown in FIG. 2, each of the upper end portion 104 and the lower end portion 105 has a bevel, and the bevel may alternatively be not set in another embodiment.

In the embodiment shown in FIG. 4, the rubber cylinder 10 is overall cylindrical. The rubber cylinder 10 has a through hole 103 located at the centre. The through hole 103 is formed being defined by an inner surface 102. An outer surface 101 is located on an outer side of the through hole 103 corresponding to the inner surface 102. When the first axial pressure F₁ acts on the upper end portion 104 in the first axial direction A or the second axial pressure F₂ acts on the lower end portion 105 in a second axial direction B, the rubber cylinder 10 is overall axially compressed to expand radially (having the same meaning as “deform in the radial direction”), making the outer surface 101 protrude outwardly and the inner surface 102 protrude inwardly. However, in a time order, the outer surface 101 generally protrudes outwardly first. After the first axial pressure F₁ is applied, the inner surface 102 is sealed with the central tube 30 in FIG. 1 and FIG. 2, and the outer surface 101 is sealed with the casing 40 in FIG. 1 and FIG. 2. Generally, the inner surface 102 and the central tube 30 have a relatively small gap (are nearly attached to each other), and the outer surface 101 and the casing 40 have a relatively large gap. The central tube 30 and the casing 40 respectively restrict the sizes of the largest protrusions of the inner surface 102 and the outer surface 101. Therefore, the degree of an outward protrusion on the outer surface 101 is greater than the degree of an inward protrusion on the inner surface 102.

As discussed above, the upper end portion 104, the lower end portion 105, and the middle portion 106 should all have elasticity. However, in the embodiments shown in FIG. 2 and FIG. 4, a hardness of the upper end portion 104 is greater than a hardness of the middle portion 106. Therefore, when the upper end portion 104 bears the first axial pressure F₁, the deformation of the middle portion 106 in the radial direction is greater than the deformation of the upper end portion 104 in the radial direction.

The hardness of the upper end portion 104 is greater than the hardness of the middle portion 106. In this case, when the upper end portion 104 is subject to the first axial pressure F₁, the upper end portion 104 more likely transfers the first axial pressure F₁ to the middle portion 106 and the lower end portion 105 instead of deforming radially itself. In this way, the middle portion 106 and the lower end portion 105 can deform radially when a relatively small first axial pressure F₁ is used, so as to achieve an overall seal of the rubber cylinder 10. The inventors find in experiments that if the hardness of the upper end portion 104 is not greater than the hardness of the middle portion 106, when the upper end portion 104 is subject to the first axial pressure F₁, the first axial pressure F₁ is more likely used to make the upper end portion 104 deform radially instead of being transferred to the middle portion 106 and the lower end portion 105. As shown in FIG. 3, the upper end portion 104 generates a large extruded shoulder 107. When the second axial pressure F₂ is then applied, the upper end portion 104 ruptures at the extruded shoulder 107 shown in FIG. 3.

According to the technical solution of the present application, if the hardness of the middle portion 106 is kept unchanged, in the present application, the hardness of the upper end portion 104 is set to be greater than the hardness of the middle portion 106. In this way, when being subject to the effect of the same first axial pressure F₁, the deformation of the upper end portion 104 in the radial direction is relatively small. It should be particularly noted that, the extruded shoulder 107 correspondingly formed by the upper end portion 104 due to radial deformation is also relatively small. The relatively small extruded shoulder 107 can effectively prevent the rubber cylinder 10 from rupturing, thereby achieving the effect of preventing the seal of the rubber cylinder 10 from failing.

The radial deformation of the upper end portion 104 is relatively small. Therefore, it is highly likely that in this case the deformation of the upper end portion 104 in the radial direction is already insufficient for sealing the casing 40 and the central tube 30. That is, in this case, the upper end portion 104 no longer produces a sealing effect, but instead, only transfers the first axial pressure F₁ applied to the upper end portion 104 to the middle portion 106 and the lower end portion 105. This is one major difference between the rubber cylinder 10 of the present application and a rubber cylinder in the prior art. Moreover, even if the radial deformation of the upper end portion 104 is relatively large to seal the casing 40 and the central tube 30, in this case, the seal of the upper end portion 104 is also only a supplement to the seal of the rubber cylinder 10. Regardless of whether the upper end portion 104 produces a sealing effect, by setting the hardness of the upper end portion 104 to be greater than the hardness of the middle portion 106, the rubber cylinder 10 is prevented from rupturing because the extruded shoulder 107 is excessively large, and a relatively small first axial pressure F₁ can also be used to seal the rubber cylinder 10.

According to the technical solution of the present application, if the hardness of the middle portion 106 is kept unchanged, in the present application, the hardness of the upper end portion 104 is set to be greater than the hardness of the middle portion 106. However, in this case, the upper end portion 104 may be not in contact with the casing 40 under the effect of the first axial pressure F₁ and fail to produce a sealing effect. In the special structure, when a hardness of the lower end portion 105 is basically the same as the hardness of the middle portion 106, the seal of the rubber cylinder of the present application is provided by the lower end portion 105 and the middle portion 106. When the hardness of the lower end portion 105 is basically the same as the hardness of the upper end portion 104, the seal of the rubber cylinder of the present application is provided by the middle portion 106. In this case, the structure for producing a sealing effect of the rubber cylinder 10 of the present application is completely different from that of the rubber cylinder in the prior art.

As a preferred embodiment, when an outer wall of the upper end portion 104 abuts an inner wall of the casing 40, more preferably, when the outer wall of the upper end portion 104 and the inner wall of the casing 40 are sealed, in this case, a lower portion of the upper end portion 104 covers an upper portion of the middle portion 106 with a basically equal area. the upper end portion 104 and the middle portion 106 are basically not different in the radial direction, so that a downward pressing effect can be produced at a joint between the middle portion 106 and the upper end portion 104, thereby preventing or reducing the extruded shoulder 107 at the joint between the middle portion 106 and the upper end portion 104.

To achieve the effect of “more likely transfers the first axial pressure F₁ to the middle portion 106 and the lower end portion 105 instead of deforming radially itself” as discussed above and the effect of preventing the extruded shoulder 107 from generating on the upper end portion 104, a metal block such as an iron block that does not deform easily can be used. However, if the metal block has a relatively small diameter, a larger extruded shoulder 107 is generated on the middle portion 106 in contact with the metal block. If the metal block has a relatively large diameter, considering bending of the casing 40, it is not easy for the metal block to slide to a suitable position in the casing 40. Moreover, if a foreign object enters the casing 40, it is also not easy to pull a relatively large metal block away from the casing. In another aspect, a metal block cannot be pulled away from the casing 40 if a lift force is relatively small, whereas the casing 40 may be damaged if the lift force is relatively large. Under comprehensive consideration, the upper end portion 104 used in the present application has elasticity, but the elasticity of the upper end portion 104 is restricted. That is, the hardness of the upper end portion 104 is greater than the hardness of the middle portion 106. In this way, the upper end portion 104 may have a relatively small diameter, so that the upper end portion 104 moves in the casing conveniently. For example, the upper end portion 104 may be the same as the diameter of the middle portion 106. Because the upper end portion 104 has a higher hardness, the extruded shoulder 107 does not form easily on the upper end portion 104 or the formed extruded shoulder 107 is relatively small. When being compressed, the upper end portion 104 gradually extends in the radial direction and deforms, and therefore a gap between the upper end portion 104 and the casing 40 is reduced, so that the size of the extruded shoulder 107 formed on the middle portion 106 is reduced or the extruded shoulder 107 is prevented from being formed on the middle portion 106.

In an embodiment, the hardness of the lower end portion 105 is greater than the hardness of the middle portion 106, so that when the lower end portion 105 bears the second axial pressure F₂, the deformation of the middle portion 106 in the radial direction is greater than the deformation of the lower end portion 105 in the radial direction. Based on the same principle, such a structure can prevent the extruded shoulder 107 from being generated when the lower end portion 105 bears the first axial pressure F₁ or the second axial pressure F₂, and can prevent the extruded shoulder 107 from becoming larger when the lower end portion 105 further bears the second axial pressure F₂ if the extruded shoulder 107 is already generated, thereby preventing the lower end portion 105 from being ruptured to cause the seal of the rubber cylinder 10 to fail.

In another embodiment, the hardness of the upper end portion 104 is basically the same as that of the lower end portion 105. That is, the hardness of the upper end portion 104 and the hardness of the lower end portion 105 are both greater than that of the middle portion 106. In this way, under either the first axial pressure F₁ or the second axial pressure F₂, the deformation of the middle portion 106 is larger than both the deformation of the upper end portion 104 and the deformation of the lower end portion 105. Such a structure can enable the middle portion 106 to rapidly reach a sealed state, and prevent the extruded shoulder 107 from occurring in the upper end portion 104 and the lower end portion 105 or preventing the extruded shoulder 107 generated in the upper end portion 104 and the lower end portion 105 from becoming larger.

In the embodiments shown in FIG. 2, FIG. 3, and FIG. 4, the rubber cylinder 10 is formed of three parts, that is, the upper end portion 104, the lower end portion 105, and the middle portion 106. Three seal rings 111 are respectively used as the upper end portion 104, the lower end portion 105, and the middle portion 106. In the embodiments shown in FIG. 6, FIG. 7, and FIG. 8, the rubber cylinder 10 is formed of eleven seal rings 111. The seal ring 111 at the highest end is used as the upper end portion 104. The seal ring 111 at the lowest end is used as the lower end portion 105. The remaining nine seal rings 111 are used as the middle portion 106. In another embodiment, there may further be another quantity of seal rings 111 forming the middle portion 106. Referring back to FIG. 2, FIG. 3, and FIG. 4, the rubber cylinder 10 may further be formed of only two seal rings 111. One seal ring 111 is used as the upper end portion 104, and the other seal ring 111 is used as the lower end portion 105 and the middle portion 106.

The shape and structure of a seal ring 111 are described below in detail.

The inventors find that because rubber cylinders 10 have different hardnesses, for example, a rubber cylinder 10 fabricated using polyether ether ketone has a relatively high hardness, the first axial pressure F₁ required to achieve setting is relatively large, in other words, the rubber cylinder 10 deforms insufficiently under a rated first axial pressure F₁, causing the rubber cylinder 10 to fail to produce a sealing effect. When a relatively soft colloid is used to fabricate the rubber cylinder 10, the rubber cylinder 10 cannot withstand a rated first axial pressure F₁ to collapse consequently or the rubber cylinder 10 can withstand the first axial pressure F₁ but still collapse when subsequently the rubber cylinder bears the second axial pressure F₂.

In resolving the problem that the rubber cylinder 10 is relatively soft, the inventors used to mix a colloid with a plurality of high-temperature high-pressure resistant filaments separate from each other. The structure can resolve to a particular degree the problem that the rubber cylinder 10 is overall slightly soft. However, the inventors further find that although the mixed filaments are all connected to the colloid, the filaments are basically not connected or are rarely connected to each other. Therefore, a hardness of the rubber cylinder 10 can only be increased in a very limited manner. Therefore, the inventors design the following technical solution: A plurality of filaments intersecting each other are used to form one base body 108, and a colloid 109 is distributed on the surface of the base body 108 and bond the filaments to form a seal ring 111. The seal ring 111 with such a structure has ductility in the radial direction. In other words, because the filaments are tangled with each other to enable the seal ring 111 to have an increased diameter within a particular range without breaking (mainly the breaking of a filament), as the diameter of the seal ring 111 becomes larger, filaments intersecting each other cancel out a part of the first axial pressure F₁ that enables the diameter of the seal ring 111 to become larger, so that if the diameter of the seal ring 111 needs to be increased to a particular degree, a larger first axial pressure F₁ needs to be provided. Especially, the colloid 109 tightly connects the intersecting filaments together. To enable the diameter of the seal ring 111 to be increased to a particular degree, a larger first axial pressure F₁ is needed. In summary, the filaments intersect to form a resisting force, and the colloid 109 bond the filaments to further form a resisting force. Under the effects of the two resisting forces, it is relatively difficult to compress the overall rubber cylinder 10. This is equivalent to that the rubber cylinder 10 becomes harder. When the seal ring 111 has an approximately the same quantity of filaments in a particular volume, the inventors find that a thickness of a seal ring can be changed to adjust the quantity of filaments intersecting each other, so that the magnitude of the required first axial pressure F₁, that is, the magnitude of a setting force applied to the rubber cylinder 10, can further be adjusted. Similarly, the quantity of filaments in a particular volume of the seal ring 111 can be increased to adjust the quantity of filaments intersecting each other, so that the magnitude of the required first axial pressure F₁ can further be adjusted. For the upper end portion 104 fabricated in both the foregoing manners, a hardness of the upper end portion 104 is greater than the hardness of the middle portion 106.

As shown in FIG. 5, the seal ring 111 comprises two parts, that is, the base body 108 and the colloid 109. For the clarity of structure, FIG. 5 only shows the colloid 109 covering the entire surface of the base body 108. For example, when the base body 108 has a circular cross section, the colloid 109 in FIG. 5 is located on the circumference of the base body 108. FIG. 5 does not show the colloid 109 that permeates in the base body 108. The base body 108 is formed by aggregating a plurality of high-temperature high-pressure resistant filaments, for example, the filament may be a glass fibre, a carbon fibre or another high-temperature high-pressure resistant material. In an embodiment, the filaments are interwoven in warp and weft to form the base body 108. In another embodiment, the filaments may further be woven in another manner to form the base body 108.

As can be learned from the foregoing description, in the technical solution of the present application, the filament does not necessarily need to have elasticity. This is because the contraction and expansion of the rubber cylinder 10 is completed by the colloid 109. As discussed above, the colloid 109 is distributed on the surface of the base bodies 108 and inside the base bodies 108, and bonds the filaments. The ideal case is that the colloid 109 bonds each filament and bonds the filaments together intersecting each other.

Referring to FIG. 4, FIG. 5, and FIG. 6, the two end portions 104 and 105 of the rubber cylinder 10 may be levelled by using the colloid 109. Each seal ring 111 is overall annular and extends in the axial direction of the rubber cylinder 10. When the colloid 109 between adjacent base bodies 108 has a same thickness, the rubber cylinder 10 should have basically a same hardness in a same area, so as to prevent the rubber cylinder 10 from collapsing locally due to uneven force distribution. However, as shown in FIG. 13, when the rubber cylinder 10 has three sections, each section of the rubber cylinder may be one separate rubber cylinder. In this way, the rubber cylinder 10 shown in FIG. 13 is equivalent to being formed by joining in the axial direction three rubber cylinders independent of each other. FIG. 13 only uses an example in which the rubber cylinder 10 has three sections. In another embodiment, the rubber cylinder may further have another quantity of sections, for example, two sections or five sections.

Because the colloid 109 covers the seal ring 111, the base body 108 of the seal ring 111 has filaments intersecting each other. The colloid 109 is distributed on the surface of the base body 108 and inside the base body 108, and bonds the filaments. First, filaments are mixed in the colloid 109. When the rubber cylinder 10 is subject to the first axial pressure F₁ or the second axial pressure F₂ to expand (inwardly and outwardly), the filament restricts the expansion, so as to increase the overall structural hardness of the rubber cylinder 10, thereby increasing the compressive strength of the rubber cylinder 10. Especially, in the case of an annular base body 108, when the seal rings 111 are subject to the first axial pressure F₁ or the second axial pressure F₂, the seal rings 111 bear relatively evenly distributed forces, thereby preventing the rubber cylinder 10 from collapsing locally. Moreover, in an embodiment of the present application, the colloid 109 between adjacent base bodies 108 has a same thickness. In this way, it can be ensured that the seal ring 111 under the effect of the first axial pressure F₁ or the second axial pressure F₂ uniformly transfers a force, thereby preventing the seal ring 111 from collapsing due to uneven force distribution on the parts of the seal ring 111.

Referring to FIG. 6, the seal rings 111 are bonded to each other by using the colloid 109 and a sum of lengths of the bonded seal rings 111 in the axial direction is equal to the length of the through hole 103, so as to form a plurality of sealed sections. A thickness of the base body 108 in FIG. 5 is 1.8 cm to 2.5 cm, and a quantity of base bodies 108 is 2 to 12. In a preferred embodiment, a quantity of the base bodies 108 is 5. In this way, the quantity of the seal rings 111 is also 5. The diameter of a filament is 7 μm to 30 μm. In this way, one seal ring 111 can have a huge quantity of filaments, so that the hardness of the rubber cylinder 10 can be greatly improved. According to experiments by the inventors, the thickness of the base body 108 preferably does not exceed 2 cm. This is because the inventors find that a colloid fluid forming the colloid 109 needs to permeate in the base body 108 to form the seal ring 111, but as the thickness of the base body 108 increases, a permeation speed of the colloid fluid gradually decreases. Especially, after the thickness of the base body 108 is greater than 2.5 cm, the permeation speed of the colloid fluid becomes very slow. Therefore, the thickness of each base body 108 is 2 cm in an embodiment, and may be 1.8 cm or 2.5 cm in another embodiment.

Referring to FIG. 6, FIG. 7, and FIG. 8 show the deformation of the rubber cylinder 10 under the first axial pressure F₁. As can be seen in FIG. 6, the colloid 109 is provided between two adjacent base bodies 108. When the rubber cylinder 10 is not subject to the first axial pressure F₁, an angle β is formed between all the base bodies 108 and the radial direction of the rubber cylinder 10. β is 10° in FIG. 6. In another embodiment, β may further be 5° or 45°. The reason of setting β in the present application lies in that when the seal ring 111 has a high overall hardness and is subject to a rated first axial pressure F₁ and as a result the rubber cylinder 10 deforms insufficiently and cannot produce a sealing effect, the seal ring 111 first turns to be parallel to the radial direction of the rubber cylinder 10 from an angle β relative to the radial direction of the rubber cylinder 10. Further, as shown in FIG. 8, a seal ring then protrudes in a radial direction. Such a structure can improve the deformation degree of the rubber cylinder 10. In the embodiment shown in FIG. 7, when the rubber cylinder 10 is not subject to the first axial pressure F₁, the base bodies 108 are all parallel to the radial direction of the rubber cylinder 10. As shown in FIG. 8, when being subject to the first axial pressure F₁, the rubber cylinders 10 shown in FIG. 6 and FIG. 7 are both shortened in the axial direction and expand in the radial direction. The second axial pressure F₂ is then applied at the lower end portion 105 of the rubber cylinder 10.

In an embodiment of the invention, the base body 108 is a graphite packing or a carbon fibre packing. A packing is usually formed by weaving relatively soft threads, and usually has a square, rectangular, or circular cross section. In an embodiment, the base body 108 has a quadrilateral cross section, and has, for example, a square cross section. In another embodiment, the base body 108 may alternatively have a circular cross section.

A constraining casing 20 of the rubber cylinder 10 is described below in detail.

Referring to FIG. 9, FIG. 10, FIG. 11, and FIG. 12, as shown in FIG. 9, the constraining casing 20 generally has a flaring form, and has a flaring end 22 and a necking end 21. Referring to FIG. 10, the flaring end 22 of the constraining casing 20 is sleeved over the upper end portion 104 and the lower end portion 105. In another embodiment, the flaring end 22 may further be sleeved over only one of the upper end portion 104 and the lower end portion 105. This mainly depends on whether the deformation of an end portion needs to be constructed to prevent an excessively large deformation during compression. In FIG. 10 to FIG. 12, a quantity of constraining casings 20 is 2. A flaring end 22 of one constraining casing 20 is sleeved over the upper end portion 104, and a flaring end 22 of the other constraining casing 20 is sleeved over the lower end portion 105. Referring to FIG. 11, the necking end 21 of the constraining casing 20 is far away from the upper end portion 104 or the lower end portion 105 that is sleeved over by the flaring end 22 and is used to bear an axial pressure. FIG. 10 and FIG. 11 schematically show a position relationship between the constraining casing 20 and other parts of the rubber cylinder 10 only for the clarity of structure. In fact, the constraining casing 20 is tightly joined with the end portion of the rubber cylinder 10. That is, the constraining casing 20 and the end portion of the rubber cylinder 10 contact each other. As can be seen in FIG. 12, after bearing the first axial pressure F₁, the constraining casing 20 is overall cylindrical. Moreover, the flaring end 22 and the necking end 21 of the constraining casing 20 have basically the same diameter, and the diameter of the flaring end 22 and the necking end 21 is the same as an inner diameter of the casing 40. In this case, the outer surface 101 of the rubber cylinder 10 is sealed with the casing 40. Moreover, the inner surface 102 of the rubber cylinder 10 is sealed with the central tube 30.

The effect of the constraining casing 20 in the present application is very important. This is because the seal rings 111 of the present application are all axially disposed, and it is also an axial pressure that produces an effect on the seal ring 111. Therefore, very likely, the seal rings 111 located at the two ends of the rubber cylinder 10 first contact the central tube 30 and the casing 40 in the radial direction under the effect of the first axial pressure F₁ or the second axial pressure F₂. As a result, a seal ring 111 located in the middle of the rubber cylinder 10 bears an excessively small force and cannot protrude radially. With the constraining of the constraining casing 20 at an end portion, the seal ring 111 in the middle can protrude first. After the seal ring 111 in the middle is restricted by the central tube 30 and the casing 40, the seal rings 111 at the two ends then protrude radially and enable the constraining casing 20 to deform in the way shown in FIG. 10, FIG. 11, and FIG. 12. Alternatively, the seal ring 111 in the middle protrudes first, and in this process, the seal rings 111 at the two ends also protrude radially and enable the constraining casing 20 to deform in the way shown in FIG. 10, FIG. 11, and FIG. 12. The foregoing two manners are both special designs developed to prevent the two ends of the rubber cylinder 10 from protruding first. When both the design of the constraining casing 20 and the design of a relatively high hardness at the upper end portion 104 appear in the rubber cylinder 10, the middle portion 106 can deform first in the radial direction errorlessly.

In the embodiments shown in FIG. 10 and FIG. 11, edges of the upper end portion 104 and the lower end portion 105 are chamfered to fit the constraining casing 20. That is, the upper end portion 104 and the lower end portion 105 that are sleeved over with the flaring ends 22 have necking forms to fit the flaring ends 22. Such a design of the rubber cylinder 10 can increase a contact area between an end portion of the rubber cylinder 10 and the constraining casing 20, and an angle is formed between an end portion in this design and the first axial pressure F₁. Therefore, a larger first axial pressure F₁ is needed to compress the rubber cylinder 10 to deform by a rated size, so that a required setting force is increased to a particular degree. As shown in FIG. 12, after the first axial pressure F₁ is applied, the rubber cylinder 10 extends inwardly and outwardly in the radial direction. Being restricted by the casing 40, in this case, the constraining casing 20 expands radially in a range defined by the casing 40. Eventually, the flaring end 22 of the constraining casing 20 becomes basically the same as the diameter of the rubber cylinder 10 and basically the same as an inner diameter of the casing 40. As shown in FIG. 11, during compression, protrusions 60 are formed. FIG. 11 schematically shows one protrusion 60. During actual compression, the overall outer surface 101 of the rubber cylinder 10 expands outwardly as the protrusion 60. In an embodiment of the present application, the design of the constraining casing 20 is used to deliberately enable the middle of the rubber cylinder 10 to protrude faster than two ends of the rubber cylinder 10. It is very important that if a material that does not deform easily is chosen for the constraining casing 20, as shown in FIG. 11, when compression continues, the protrusion 60 contacts an upper edge of the constraining casing 20, and the protrusion 60 is eventually sheared. As a result, the seal of the rubber cylinder 10 is affected. A copper casing is chosen for the constraining casing in the present application, and it is restricted that a maximum thickness of the flaring end 22 does not exceed 2 mm. The flaring end 22 means, for example, an entire horn-shaped edge shown in FIG. 9 rather than the end surface on the rightmost side in FIG. 9. Such a restriction can prevent the constraining casing 20 from damaging the protrusion 60 or allows only a slight damage to the protrusion 60. Moreover, during compression, the casing 40 deforms for the constraining casing 20 as shown in FIG. 12. Based on the same idea, the right-angle type constraining casing 20 shown in FIG. 12 cannot be used before compression. Otherwise, during compression, the constraining casing 20 also shears the gradually protruding outer surface 101 to make the rubber cylinder 10 rupture. In the present application, the constraining casing 20 has a horn opening form. During compression, the constraining casing 20 and the protrusion 60 have a surface contact rather than a line contact, thereby greatly reducing the possibility of damaging the protrusion 60. As shown in FIG. 9, the necking end 21 has an inward chamfer. The chamfer surrounds the central tube 30 during compression, and the chamfer receives the first axial pressure F₁. Such a design can enable the compression casing 20 to deform in an orderly and gradual manner instead of collapsing suddenly under the first axial pressure F₁. Another important reason of choosing a copper casing for the constraining casing 20 in the present application lies in that in this way, when a packer 200 is removed from a downhole, the copper casing deforms easily and does not get stuck in the casing 40. Based on the same idea, silver that also deforms easily can also be chosen for the constraining casing.

The invention further provides a packer, the packer having the rubber cylinder 10 defined in one of the foregoing technical solutions.

The invention further provides a bridge plug, the bridge plug having the rubber cylinder 10 defined in one of the foregoing technical solutions.

The embodiments in this specification are all described in a progressive manner, mutual reference may be made to the same or similar parts of the embodiments, and each embodiment focuses on description of differences from other embodiments. In particular, the system embodiment is basically similar to the method embodiment and therefore is described simply, and for a related part, reference may be made to the part of the description of the method embodiment.

The object, technical solution and beneficial effects of the present invention are further described in detail by the above-mentioned particular examples; and it is to be understood that the above-mentioned contents are merely particular embodiments of the present invention, and are not used to limit the present invention, and wherever within the spirit and principle of the present invention, any modifications, equivalent replacements, improvements etc., shall be all contained within the scope of protection of the present invention.

Furthermore, it should be noted that the language used in the description is selected mainly for the purpose of readability and teaching, but is not selected for explaining or defining the subject matter of the invention. Therefore, for those of ordinary skilled in the art, many modifications and variations are all obvious without departing from the scope and spirit of the appended claims. For the scope of the invention, the disclosure of the invention is illustrative but not restrictive, and the scope of the invention is defined by the appended claims. 

1: A rubber cylinder comprising: a through hole located at the center, an inner surface located at the through hole (103), an outer surface corresponding to the inner surface, an upper end portion and a lower end portion respectively located at two ends of the rubber cylinder (10), and a middle portion located between the upper end portion and the lower end portion, the upper end portion being used to bear a first axial pressure in an axial direction, and the lower end portion being used to bear a second axial pressure opposite to the first axial pressure in the axial direction; when the first axial pressure is applied to the upper end portion, the upper end portion, the middle portion, and the lower end portion all deforming in a radial direction; and when the second axial pressure is applied to the lower end portion, the upper end portion, the middle portion, and the lower end portion (105) all deforming in the radial direction, wherein, a hardness of the upper end portion (104) is greater than a hardness of the middle portion, so that when the upper end portion bears the first axial pressure, the deformation of the middle portion in the radial direction is greater than the deformation of the upper end portion in the radial direction. 2: The rubber cylinder according to claim 1, wherein, a hardness of the lower end portion is greater than the hardness of the middle portion, so that when the lower end portion bears the second axial pressure, the deformation of the middle portion in the radial direction is greater than the deformation of the lower end portion in the radial direction. 3: The rubber cylinder according to claim 1, wherein, the hardness of the upper end portion is basically the same as a hardness of the lower end portion, so that when the upper end portion bears the first axial pressure, the deformation of the middle portion in the radial direction is greater than the deformation of the upper end portion in the radial direction and the deformation of the lower end portion in the radial direction, and when the lower end portion bears the second axial pressure, the deformation of the middle portion in the radial direction is greater than the deformation of the upper end portion in the radial direction and the deformation of the lower end portion in the radial direction. 4: The rubber cylinder according to claim 1, wherein, the rubber cylinder is formed of more than two seal rings arranged in the axial direction. 5: The rubber cylinder according to claim 4, wherein, the rubber cylinder is formed of two seal rings arranged in the axial direction, one seal ring is used as the upper end portion, and the other seal ring is used as the lower end portion and the middle portion; or the rubber cylinder is formed of three seal rings arranged in the axial direction, the three seal rings are respectively used as the upper end portion, the middle portion, and the lower end portion; or the rubber cylinder is formed of more than three seal rings arranged in the axial direction, two seal rings distributed on the two ends in the axial direction are respectively used as the upper end portion and the lower end portion, and the remaining seal ring is used as the middle portion. 6: The rubber cylinder according to claim 5, wherein, each of the seal rings has a colloid and an annular base body, the base body is formed of a plurality of high-temperature high-pressure resistant filaments intersecting each other, the colloid bonds all the filaments, and the colloid is distributed on surfaces of the base bodies, so that the inner surface and the outer surface are respectively formed on the inside and outside of the plurality of seal rings arranged in the axial direction. 7: The rubber cylinder according to claim 6, wherein, the base body is a graphite packing or a carbon fibre packing; and preferably, an angle β is formed between each of the seal rings and the radial direction of the rubber cylinder, wherein 5°≤β≤45°. 8: The rubber cylinder according to claim 1, further comprising: a constraining casing, wherein the constraining casing generally has a flaring form, a flaring end of the constraining casing is sleeved over the upper end portion or the lower end portion, a necking end of the constraining casing is far away from the upper end portion or the lower end portion that is sleeved over by the flaring end and used to bear the first axial pressure or the second axial pressure; preferably, the necking end has an inward chamfer; and preferably, the upper end portion or the lower end portion sleeved over by the flaring end has a necking form to fit the flaring end; preferably, the constraining casing is made of copper, and a maximum thickness of the flaring end is less than or equal to 2 mm; preferably, a quantity of the constraining casings is 2, wherein the flaring end of one constraining casing is sleeved over the upper end portion, and the flaring end of the other constraining casing is sleeved over the lower end portion. 9: A packer, comprising: a rubber cylinder, wherein the rubber cylinder has a through hole located at the center; an inner surface located at the through hole; an outer surface corresponding to the inner surface; an upper end portion and a lower end portion respectively located at two ends of the rubber cylinder, and a middle portion located between the upper end portion and the lower end portion, the upper end portion is used to bear a first axial pressure in an axial direction, and the lower end portion is used to bear a second axial pressure opposite to the first axial pressure in the axial direction; when the first axial pressure is applied to the upper end portion, the upper end portion, the middle portion, and the lower end portion all deform in a radial direction; and when the second axial pressure is applied to the lower end portion, the upper end portion, the middle portion, and the lower end portion all deform in the radial direction; and wherein a hardness of the upper end portion is greater than a hardness of the middle portion, wherein, when the upper end portion bears the first axial pressure, the deformation of the middle portion in the radial direction is greater than the deformation of the upper end portion in the radial direction. 10: A bridge plug, comprising: a rubber cylinder, wherein the rubber cylinder has a through hole located at the center; an inner surface located at the through hole; an outer surface corresponding to the inner surface; an upper end portion and a lower end portion respectively located at two ends of the rubber cylinder, and a middle portion located between the upper end portion and the lower end portion, the upper end portion is used to bear a first axial pressure in an axial direction, and the lower end portion is used to bear a second axial pressure opposite to the first axial pressure in the axial direction; when the first axial pressure is applied to the upper end portion, the upper end portion, the middle portion, and the lower end portion all deform in a radial direction; and when the second axial pressure is applied to the lower end portion, the upper end portion, the middle portion, and the lower end portion all deform in the radial direction; and wherein a hardness of the upper end portion is greater than a hardness of the middle portion, so that when the upper end portion bears the first axial pressure, the deformation of the middle portion in the radial direction is greater than the deformation of the upper end portion in the radial direction. 